The aim of this study is to examine the feeding and social organization of Colobus badius preussi in the Korup Forest Reserve, Cameroon, relative to the secondary chemistry of that forest. Preliminary analysis from a comprehensive ecological survey have indicated that the secondary chemistry of Korup is similar to the previously studied Douala-Edea forest, containing a population of Colobus satanas, and dissimilar from Kibale Forest, Uganda, which contains a population of Colobus badius tephrosceles and provides baseline data. Ecological aspects of Kibale have been analysed using our methods. It is anticipated that the mature leaves of all the common tree species at Korup will possess high levels of secondary compounds and particularly of phenolic compounds such as condensed tannins. Condensed tannins reduce the digestibility of leaves and of their new energy production. It is predicted that the mature leaves of Korup will provide only a minor fraction of the diet of Colobus, in marked contrast to Kibale. However, seeds might not be possible as a year-round diet item, as community-wide crop failures are common and up to 95% of trees can fail to produce seeds in any given year. It is anticipated that the diet of C. badius will comprise seeds and those leaves that are low in phenolic compounds such as some young leaves and the vegetation of light gaps and river banks. But a diet of this nature is more patchily distributed in space and time than is a diet of mature leaves. It is predicted therefore that the home range of the Korup population will be larger than at Kibale, daily foraging distances will be greater and seasonal movements more marked. The population density of C. badius at Korup will be much less than that of Kibale. There will also be a greater vertical distribution and they will be found to utilize the lower storeys of the forest, particularly light gaps and river banks. The results of these ecological constraints will be that group size at Korup will be smaller than at Kibale, groups will be more dispersed during foraging and social interactions will be reduced.